Seroprevalence and Correlates of SARS-CoV-2 Antibodies in Health Care Workers in Chicago

John T. Wilkins*, Elizabeth L. Gray, Amisha Wallia, Lisa R. Hirschhorn, Teresa R. Zembower, Joyce Ho, Naomi Kalume, Ojoma Agbo, Alex Zhu, Laura J. Rasmussen-Torvik, Sadiya S. Khan, Mercedes Carnethon, Mark Huffman, Charlesnika T. Evans

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

31 Scopus citations


Background: Identifying factors associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection among health care workers (HCWs) may help health systems optimize SARS-CoV-2 infection control strategies. Methods: We conducted a cross-sectional analysis of baseline data from the Northwestern HCW SARS-CoV-2 Serology Cohort Study. We used the Abbott Architect Nucleocapsid IgG assay to determine seropositivity. Logistic regression models (adjusted for demographics and self-reported community exposure to coronavirus disease 2019 [COVID-19]) were fit to quantify the associations between occupation group, health care delivery tasks, and community exposure and seropositive status. Results: A total of 6510 HCWs, including 1794 nurses and 904 non-patient-facing administrators, participated. The majority were women (79.6%), 74.9% were White, 9.7% were Asian, 7.3% were Hispanic, and 3.1% were non-Hispanic Black. The crude prevalence of seropositivity was 4.8% (95% CI, 4.6%-5.2%). Seropositivity varied by race/ethnicity as well as age, ranging from 4.2% to 9.6%. Out-of-hospital exposure to COVID-19 occurred in 9.3% of HCWs, 15.0% (95% CI, 12.2%-18.1%) of whom were seropositive; those with family members diagnosed with COVID-19 had a seropositivity rate of 54% (95% CI, 44.2%-65.2%). Support service workers (10.4%; 95% CI, 4.6%-19.4%), medical assistants (10.1%; 95% CI, 5.5%-16.6%), and nurses (7.6%; 95% CI, 6.4%-9.0%) had significantly higher seropositivity rates than administrators (referent; 3.3%; 95% CI, 2.3%-4.4%). However, after adjustment, nursing was the only occupation group with a significantly higher odds (odds ratio, 1.9; 95% CI, 1.3-2.9) of seropositivity. Exposure to patients receiving high-flow oxygen therapy and hemodialysis was significantly associated with 45% and 57% higher odds for seropositive status, respectively. Conclusions: HCWs are at risk for SARS-CoV-2 infection from longer-duration exposures to people infected with SARS-CoV-2 within health care settings and their communities of residence.

Original languageEnglish (US)
Article numberofaa582
JournalOpen Forum Infectious Diseases
Issue number1
StatePublished - Jan 1 2021


  • COVID-19
  • SARS-CoV-2
  • health care workers
  • serology

ASJC Scopus subject areas

  • Clinical Neurology
  • Oncology


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